Non-woven fabrics and a process for treating the same



United States Patent Office 3,291,677 Patented Dec. 13, 1966 NON-WOVEN FABRICS AND A PROCESS FOR TREATING THE SAP/IE Herbert W. Coates, Joseph F. Baigas, Jr., Milon J. Hamilton, and John T. Haynes, Jr., Charlotte, N.C., assignors to Kern-Wave Industries, Inc, a corporation of North Carolina No Drawing. Filed Nov. 2, 1964, Ser. No. 408,339

6 Claims. (Cl. 161170) This invention relates to compacted non-woven fabrics which may be subsequently restored or rejuvenated to substantially the originally bonded dimensions thereof and more particularly to a process by which nonwoven fabric may be compacted and subsequently restored without causing any harmful effects to the non-woven fabrics.

Non-woven fabrics of the type utilizing fibers coated with adhesive or binder to form a self supporting porous batt have found wide utility in domestic, manufacturing and industrial operations, such as floor maintenance, kitchen scouring, interlinings for clothing, air or gas filters, packaging materials, etc. These non-woven fabrics are generally constructed of a plurality of fibers, either straight or curled, of various lengths, held in threedimensional arrangement by means of an adhesive or resinous binder. The fibers are generally substantially coated with this binder and are joined together at the points where the fibers cross and intersect by the resinous binder or adhesive to form an open, low density, non-woven batt.

These open, non-Woven batts are often fabricated into the desired products by the manufacturers thereof or are sold in rolls to other manufacturers for subsequent fabrication into desired products. These final products are often made or fabricated from the non-woven batts alone or are combined with other materials or fabrics by stitching, laminating, etc. according to the end use desired. These end products often contain other materials internally thereof such as soaps, abrasives, fillers, etc.

Due to the bulky nature of these highly porous non- Woven batts, storage and shipping has long been a problem with the manufacturer, with the fabricator and with the consumer of the non-woven fabrics. During shipping and storing of these non-woven fabrics or the products made therefrom, space has been a relevant factor inasmuch as the bulky, highly porous, non-woven [fabrics or products made thereform occupy a large area while being relatively light in weight.

It is therefore an object of this invention to overcome the problem of space required for both storing and shipping of non-woven fabrics and the products made therefrom. This object is accomplished by providing a process whereby the non-woven fabrics or products made therefrom may be compacted during or following manufacture thereof to reduce their dimensions or bulk and thereby require less space for shipping and storing and may be subsequently restored or rejuvenated to substantially their original dimensions at any desired time according to the ultimate use of the non-woven fabrics.

Compaction of the non-woven fabrics not only solves the space problem during storing and shipping, but also provides distinct advantages in the fabrication of the non-woven fabrics into the commercial products thereof. It is evident that non-woven fabrics of this type are more easily handled, cut, stitched, laminated, molded, etc. when in the compacted state as opposed to the bulky porous non-compacted original state.

Therefore, it is a further object of this invention to provide a non-Woven fabric which has been compacted from the originally bonded state thereof to form'a less open, higher density fabric than originally formed to aid in handling and fabricating and which may be subsequently restored to substantially the originally bonded, more open, low density state thereof.

By this invention it has been discovered that non-woven fabrics, comprising a plurality of thermoplastic fibers disposed in intermingled, three dimensional arrangement throughout the length, width and depth of the (fabric and bonded together at spaced points by a resinous bonding material to fixedly join the fibers together to form an integral non-woven fabric structure, may .be heated to temperatures below the plastic flow temperatures of both the fibers and of the resinous bonding material for a limited period of time and then subsequently compacted by applying pressure to the heated non-Woven fabrics and cooling under pressure. The non-woven fabrics will retain this compacted state for an indefinite period of time.

Restoration or rejuvenation 'of these compacted nonwoven fabrics may be accomplished by a subsequent heating of the compacted non-woven fabrics to temperatures below the plastic flow temperatures of both the fibers and the resinous bonding material utilized therein for a limited period of time. This restoration will normally permit the non-woven fabrics to regain at least their originally bonded dimensions and sometimes greater dimensions. However, it is possible to restore these non-woven [fabrics to dimensions less than the originally bonded dimensions if desired.

The above compaction and restoration is possible because during the processing and bonding of non-woven fabrics of the type utilizing thermoplastic fibers, a stress-strain relationship is set up in the fibers by the bonding thereof with a resinous bonding material and this stress-strain relationship produces tension and/or compression in the fibers which is held by the resinous bonding material. Upon heating of the bonded nonwoven fabrics, these stresses and strains are relaxed and the fibers, being more plastic when heated, conform readily to the compressing forces. Upon cooling under pressure, the non-woven fabrics retain their new compressed state when the pressure is removed. The retention by the non-woven fabrics of this new compressed state is believed to be caused by a temporary or false crimp being set in the fibers and a temporary set being formed by the bonding material. This false crimp of the fibers and temporary set of the bonding material produced by the compressing force imposes new stresses and strains on the fibers which are built into the compressed fabrics after cooling.

Upon restoration by reheating of the compressed nonwoven fabrics, these new stresses and strains are relaxed by the heat and the fibers tend to straighten out to their old configuration. A further and perhaps more important reason for the straightening out of the fibers to their old configuration is the fact that the bonding material acts as guides to return the fibers to their originally bonded condition. During this subsequent heating of the compacted non-woven fabrics, the false crimp in the fibers is released and the temporary set of the bonding material is released. The fact that thermoplastic fibers are originally produced straight and always have a desire to return to their straight position is a further property which assists the restoration process of this invention and sometimes causes the non-woven fabric to assume greater dimensions than originally produced.

Also, most fibers are heat set by the producer at a temperature higher than the temperature to which the fibers are subjected during bonding and higher than the temperature at which the compaction process is performed. This helps the fibers in returning to at least their normal position within the bonded web structure.

It is important that the temperature utilized for compaction of the bonded non-woven fabrics does not exceed .the plastic flow point of the resin because if the temperature does exceed this plastic flow point, the resin will become sticky and will rebond at other fiber points holding the compacted non-woven fabrics in their compacted state. It is also important that the temperature utilized for compaction does not exceed the plastic flow point of the fibers because if the temperature does exceed this plastic flow point a substantially permanent stress-strain relationship will be set up in the fibers and the fibers will be given a permanent crimp which will hold the non-woven fabrics in their compacted state and prevent rejuvenation.

The compaction and restoration process of this invention is applicable to any bonded non-woven fabrics utilizing thermoplastic fibers therein, especially fibers selected from the group consisting of polyester, nylon, acrylic, acetate, m-odacryli-c, triacetate, polypropylene, polyethylene or combinations thereof and which are bonded with any resinous bonding material, especially those bonding materials selected from the group consisting of acrylic, Vinyl, melamine, polyvinyl chloride, polyvinyl acetate, butadiene styrene, butadiene acryl-onitrile, melamine formaldehyde, urea formaldehyde, phenol formaldehyde, polyvinylidene chloride, epoxy type resins or combinations thereof.

The compaction step of this process may be performed by heating the non-woven fabrics in any suitable manner during manufacture or following manufacture, such as in an oven, with infrared heat or the like, by compacting under pressure by any convenient means, such as pressure rolls, calendar rolls or the like and by cooling under pressure by any convenient means, such as exposure to the atmosphere. Likewise, the restoration step may be preformed. by heating the compacted non-woven fabrics in any suitable manner, such as an oven, infrared heat, oils, hot minerals, water, sun light or the like. In the case of certain products made from these nonwoven fabrics, it has been found that the restoration step may be accomplished by theconsurner by subjecting these products 4 to heat obtained from hot water in the ordinary kitchen sink.

It has been found that the compaction and restoration process of this invention is better performed on nonwoven fabrics made from the above fibers and bonded with the above bonding materials when the initial heating forming part of the compaction step is performed within the temperature range of F. to 450 F. for a period of time between less than 1 sec. and 10 min. The preferred pressure for compacting these non-Woven fabrics tollowing heating thereof is between 1.0 psi. and 25.0 psi. for a period of time from less than 1 sec. to 10 sec. The cooling is accomplished during the period of compaction.

When performing the compaction step within these ranges of temperature, time and pressure, it has been found that the non-woven fabrics will be compacted to from about 99% to 4% of their original volume and are capable of rejuvenation of from about 1% to 1700% of their compacted volume. In the compacted state, these non-woven fabrics will contain anetw-ork of intercommunicating voids which comprise not more than about 74.3% of the volume of the non-woven fabric. The network of intercomnrunicating voids comprises not less than about 75% of the volume of the non-woven fabrics when the fabric is in the rejuvenated or originally bonded state.

The subsequent restoration of the compacted nonwoven fabrics made from the above types of fibers bonded with the above types of bonding materials is better performed by heating the compacted fabrics to a temperature between 125 F. and 450 F. for a period of time between less than 1 sec. and 10 min.

These preferred ranges for the compaction and restoration process Will be more fully realized from the following specific examples of types of non-woven fabrics, and the compaction and restoration processes used thereon, giving the types of fibers and the bonding materials used to form the non-Wovenfabrics, original igau-ges of the non-Woven fabric before compaction, temperatures and times (used for initial heating steps before compaction, pressures and times used for compaction, igau'ges of the non-woven fabric after compaction, temperatures and times used for restoration, and gauges of the materials after restoration.

Example 1 A non-woven fabric is formed from 33 /3 6.0 d.p.-f. crimped staple Kodel polyester 2" cut fibers, 33% 4.5 d.p.f. Fortrel polyester 2 cut fibers, and 3'3 /a% waste polyester fibers. These fibers are formed into an open, non-Woven, threedimensional web in any conventional manner, such as by a Rando-Webber machine, commercially available from the Curlator Corporation of Rochester, New York, Proctor-Form and Duo-Form machines, commercially available from Proctor and Swartz Company of Philadelphia, Pa., Web Former machine, commercially available from James H. Hunter Company of North Adams, Mass, conventional carding and 'garnetting machines, etc. The fibers in this web are bonded together at spaced points with a bonding material comprising 81.25% unplasticized polyvinyl chloride Geon 354 resin and 18.75% of emulsified tri cresyl phosphate plasticizer to torm an integral non-woven fabric structure by any conventional method, such as passing the web through one or more spray booths and spraying the bonding material thereon, emersing the web in a bath of bonding material and extracting the excess, etc. This non-woven fabric may be compacted and subsequently restored at any time under the following conditions with the following results:

7 Compaction Step Restoration Step Heating Compacting Gauge Heating Gauge Original After After Gauge Com- Res toin Mils Temp., Time. Pressure, Time, paction Temp, Time, ration 13. min. p.s.i. sec. in Mils F. In Mils 640 325 1% 10 10 63 325 2% m in 580 664 325 1% 10 10 54 348 1% rnm 650 650 325 1% 10 10 100 300 l m n. 10 sec 660 730 325 1% l 49 248 1 min. 45 sec- 440 730 325 1% 10 10 49 248 2 mm. 30 sec 600 671 325 1% 10 10 49 200 5 min 326 A non-woven fabric is formed, as in Example 1, from 33 /3% d.p-f. Acrilan staple 2 /2" cut fibers, 33 /s% 15 dimensions. However, this non-woven fabric may be restored to dimensions less than the original dimensions under certain temperatures and times if such be desired.

Example 3 A non-woven fabric is formed, as in Example 1, from 40% 5.2 d.p.f. Kodel fiberfill polyester 1 /2 cut fibers and 60% 15.0 d.p.f. Kodel polyester 2" cut fibers. The fibers are bonded, as in Example 1, with a bonding material comprising 99.9% of a self cross-linking copolymer acrylic Rhoplex HA 16 resin and .1% Deceresol N1 wetting agent. This non-woven fabric may be compacted and subsequently restored at any time under the following conditions with the following results:

Compaction Step Restoration Step Heating Compacting Gauge Heatin Gau 6 Original After g Afte i Gauge Com- Restoin Mils Temp Time. Pressure, Time, paction Temp., Time ration F. 111111. p.s.i. sec. in Mils F. In Mils 556 325 1% 10 10 100 320 546 430 325 1% 1 0 10 68 345 465 567 325 1% 10 10 93 300 550 465 325 1% 10 1O 92 250 437 465 325 1% 10 10 92 250 450 465 325 1% l 0 10 92 250 460 465 325 1% 10 10 92 250 475 480 325 1 10 10 85 200 482 480 325 1 10 10 85 200 2 min. sec- 482 505 325 1% 10 10 97 145 5 min 425 6.0 d.p.f. crimped staple Kodel polyester 2 cut fibers, and 33 /s% 15 d.p.f. orimped staple Verel modacrylic 1 /2" cut fi-bers. These fibers are bonded, as in Example 1, with a bonding material comprising 90% unplasticized polyvinyl chloride Geon 354 resin and 10% of tri cresyl phosphate plasticizer. This nonwoven fabric may be compacted and subsequently restored at any time under the following conditions with the following results:

Compaction Step Restoration Step Heating Compacting Gauge Heating Gauge Original After After Gauge Com- Restoin Mils Temp., Time. Pressure, Time, paction Temp, Time, ration F. min. p.s.i. sec. in Mils F. In Mils 497 325 1% 10 10 320 590 468 325 1% 10 10 44 348 538 494 325 1% 10 10 31 300 410 478 325 1% 10 10 40 300 580 485 325 1% 10 10 46 247 1 min 40 sec l 452 485 325 1% 1O 10 46 247 2 min. 30 sec- 498 515 325 1% 10 10 37 200 3 min. 30 sec- 277 515 325 1% 10 10 37 210 5 min 250 From these tests it was determined that the most favorable restoration is acoomplished in the temperature range of 250 F.-350 F. for a period of time from 20 sec. to 2 min. 30 sec. These more favorable ranges of temperatures and times will restore the non-woven fabric to at least the original dimensions thereof and sometimes greater 70 stored to dimensions less than the original dimensions under certain temperatures and times if such be desired. Example 4 A non-woven fabric is formed, as in Example 1, from 5.2 d.p.f. Kodel fiberfill polyester 1%" cut fibers. The fibers are bonded, as in Example 1, with a bonding naterial comprising 100% of a self cross-linking copolyner acrylic Rhoplex HA 16 resin. This non-Woven fabric nay be compacted and subsequently restored at any time mder the following conditions with the following results:

From these tests it was determined that the most favorable restoration is accomplished in the temperature range of 200 F.345 F. for a period of time from 8 sec. to 45 sec. These more favorable ranges" of temperatures and times will restore the non-Woven fabric to at least Compaction Step Restoration Step Heatin Compacting Gauge Heating Gauge Original g After After Gauge Com- Restoin Mils Temp., Time. Pressure, Time, paetion Temp., Time ration F. min. p.s.i. see. in Mils F. In Mils From these tests it was determined that the most favorable restoration is accomplished in the temperature range of 200 F.340 F. for a period of time from 1 sec. to sec. These more favorable ranges of temperatures and times will restore the non-woven fabric to at least the original dimensions thereof and sometimes greater dimensions. However, this non-Woven fabric may be restored to dimensions less than the original dimensions under certain temperatures and times if such be desired.

Example 5 A non-woven fabric is formed, as in Example 1, from 100% 15 denier nylon staple 2 cut fibers. These fibers are bonded, as in Example 1, with a bonding material comprising 11.25% of a self cross-linking copolymer the original dimensions thereof and sometimes greater dimensions. However, this non-woven fabric may be restored to dimensions less than the original dimensions under certain temperatures and times if such be'desired.

Example 6 Compaction Step Restoration Step Heating Compacting Gauge Heating Gauge Original After After Gauge Com- Rest). in Mils Temp, Time. Pressure, Time, paction Temp., Time ration F. min. p.s.i. sec. in Mils F. In Mils 108 325 1% 10 1O 320 122 125 325 1% 10 10 57 350 142 132 325 1% 10 10 54 300 142 136 325 1% 10 10 59 250 137 117 325 1% 10 10 62 200 110 117 325 1% 10 10 62 200 123 155 325 1% 10 10 83 144 144 128 325 13/ 10 10 61 150 5 min 116 acrylic Rhoplex HA 16 resin, 8.75% of a pl-asticized polyvinyl chloride Geon 576 resin, 27.75% of a melamine formaldehyde Aerotex MM resin, and 52.25% of an inert filler. This non-woven fabric may be compacted and subsequently restored at any time under the following conditions with the following results:

10 sec. These more favorable ranges of temperatures and times will restore the non-woven fabric to at least the original dimensions thereof and sometimes greater Compaction Step Restoration Step Heating Compacting Gauge Heating Gauge Original After After Gauge Corn- Restoin Mils Temp., Time. Pressure, Time, paction Temp., Time ration F. min. p.s.i. sec. in Mils F. In Mils 270 325 1% 10 10 320 254 L 270 325 1% 1O 10 75 320 258 j: 250 325 1% 10 10 76 345 252 230 325 1% 10 10 69 300 352 240 325 1% 10 10 73 250 225 231 325 13 10 10 250 238 202 325 1% 10 10 68 200 197 202 325 1% p 10 1O 68 200 207 249 325 1% 10 10 65 158 1 min. 30 sec. 198 249 325 P 10 10 65 152 2 min 219: 249 32a 1% 10 10 65 2min. 30 sec- 225 249 325 1% 10 10 65 144 3 min .,.c 228 249 325 1% 10 10 65 144 5 min 229 245 325 1% 10 10 72 147 5 min 225 dimensions. However, this non-woven fabric may be restored to dimensions less than the original dimensions under certain temperatures and times if such be desired.

From the above specific examples, it may be seen that satisfactory compaction and restoration of these nonwoven fabrics may be performed within a wide range of temperatures and times and thus a very flexible process has been found by this invention which may be utilized by the non-woven fabric manufacturer, fabricator and/ or consumer without the necessity for specilized equipment. A somewhat modified form of the process of this invention may be found useful to manufacturers of non-woven fabrics of the type discussed above or others utilizing non- Woven fabrics of this type. This modified process utilizes cold compaction rather than hot compaction, as discussed above. Under these conditions, a continuous web or other forms of non-woven fabrics may be wound or packaged under pressure in the compressed state following manufacture thereof and held in this compressed state by the roll or package. During this holding of the non-woven fabrics in the compressed state by the roll or package, some of the forces of compression and tension are relieved and upon unwinding or unpackaging of the non-woven fabrics, the fabrics will not spring back to or recover their original dimensions or volume due to lack of energy or resilience. However, restoration of these cold compressed non-woven fabrics may be accomplished by subsequent heating for a limited period of time of the non-woven fabrics, as discussed above, to a temperature below the plastic flow temperatures of both of the fibers and the resinous bonding material used in the non-Woven fabrics.

The compaction and restoration process of this invention may also be utilized, as discussed above, when combining non-woven fabrics with other types of materials, such as lamination of the non-woven fabrics to another material wherein the compaction may be performed before lamination, during lamination or following lamination and restoration may be accomplished at any convenient time thereafter. Compaction may also be performed before, during or after stitching or otherwise securing the non-woven fabrics to other types of materials with restoration following at a convenient time according to the use desired.

Therefore, it may be seen that the compaction and restoration process of this invention for non-woven fabrics utilizing thermoplastic fibers and resinous bonding materials and the compacted non-woven fabric which may be subsequently restored or rejuvenated have wide utility by the manufacture, fabricator and/or consumer of these non-woven fabrics. The process or either step thereof may be utilized at any convenient time according to the use to which the non-woven fabrics are to be subjected.

The present invention has been described in detail above for purposes of illustration only and is not intended to be limited by this description or otherwise except as defined in the appended claims.

What is claimed is:

1. A process for treating an open, low density, non- Woven fabric formed from thermoplastic fibers bonded together with a resinous bonding material; said process comprising the steps of: compacting said non-woven fabric, without the addition of any bonding material, to a less open, higher density, self-sustaining compacted state, said compacting step consisting essentially of heating said non-woven fabric to a temperature below the plastic flow temperature of both said thermoplastic fibers and said resinous bonding material, applying pressure to said heated non-woven fabric and cooling said heated and compacted non-woven fabric; and subsequently restoring said compacted non-woven fabric to substantially the original dimensions thereof, said restoring step comprising heating said compacted non-woven fabric to a tem- 10 perature below the plastic flow temperatures of both said thermoplastic fibers and said resinous bonding material; whereby said non-Woven fabric in the compacted state may be more readily stored, shipped, fabricated, etc. and may be subsequently restored at any convenient time for the desired use thereof.

2. A process, as set forth in claim 1, in which said heating of said non-woven fabric during the compaction step comprises heating to a temperature between F. and 450 F. for a period of time from less than one second to ten minutes. 'l

3. A process, as set forth in claim 1, in which said pressure applied to said non-woven fabric is between 1.0 p.s.i. and 25.0 p.s.i. for a period of time from less than one second to ten seconds.

4. A process, as set forth in claim 1, in which said heating of said non-woven fabric during the restoration step comprises heating to a temperature between 125 F. and 450 F. for a period of time between less than one second and ten minutes.

5. A process for treating an open, low density, nonwoven fabric formed from thermoplastic fibers bonded together with a resinous bonding material; said process comprising the steps of: compacting said non-woven fabric, without the addition of any bonding material, to a less open, higher density, self-sustaining compacted state, said compacting step consisting essentially of heating said non-Woven fabric to a temperature between 125 F. and 450 P. which is below the plastic flow temperature of both said thermoplastic fibers and said resinous bonding material for a period of time from less than one second to ten minutes, applying pressure of between 1.0 p.s.i. and 25.0 p.s.i. for a period of time from less than one second to ten seconds to said heated non-woven fabric and cooling said heated and compacted non-woven fabric; and subsequently restoring said compacted non-woven fabric to substantially the original dimensions thereof, said restoring step comprising heating said compacted non-woven fabric to a temperature between 125 F. and 450 F. which is below the plastic flow temperatures of both said thermoplastic fibers and said resinous bonding material for a period of time between less than one second and ten minutes; whereby said non-woven fabric in the compacted state may be more readily stored, shipped, fabricated, etc., and may be subsequently restored at any convenient time for the desired use thereof.

6. A non-woven fabric comprising a plurality of thermoplastic fibers disposed in an intermingled, threedimensional arrangement throughout the length, width and depth of said fabric, said fibers being bonded together at spaced points by a resinous bonding material to fixedly join said fibers together to form an integral nonwoven structure, said non-woven fabric having a network of intercommunicating voids between said fibers throughout said fabric, said non-woven fabric having been compacted without the addition of any bonding material to a less open, higher density, compacted state from the state in which said fabric was originally made, and said nonwoven fabric being responsive to the application of heat thereto of a temperature below the plastic flow temperature of both said thermoplastic fibers and said resinous bonding material for expansion to generally the original more open, low density state thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,574,849 11/1951 Talalay ,161 3,000,464 9/1961 Watters 161-190 3,189,669 6/ 1965 Goldfein.

EARL M. BERGERT, Primary Examiner.

R. A. FLORES, Assistant Examiner. 

6. A NON-WOVEN FABRIC COMPRISING A PLURALITY OF THERMOPLASTIC FIBERS DISPOSED IN AN INTERMINGLED THREEDIMENSIONAL ARRANGEMENT THROUGHOUT THE LENGTH, WIDTH AND DEPTH OF SAID FABRIC, SAID FIBERS BEING BONDED TOGETHER AT SPACED POINTS BY RESNOUS BONDING MATERIAL TO FIXEDLY JOIN SAID FIBERS TOGETHER TO FORM AN INTRGRAL NONWOVEN STRUCTURE, SAID NON-WOVEN FABRIC HAVING A NETWORK OF INTERCOMMUNICATING VOIDS BETWEEN SAID FIBERS THROUGHOUT SAID FABRIC, SAID NON-WOVEN FABRIC HAVING BEEN COMPACTED WITHOUT THE ADDITION OF ANY BONDING MATERIAL TO A LESS OPEN, HIGHET DENSITY, COMPACTED STATE FROM THE STATE IN WHICH SAID FABRIC WAS ORIGINALLY MADE, AND SAID NONWOVEN FABRIC BEING RESPONSIVE TO THE APPLICATION OF HEAT THERETO OF A TEMPERATURE BELOW THE PLASTIC FLOW TEMPERATURE OF BOTH SAID THERMOPLASTIC FIBERS AND SAID RESINOUS BONDING MATERIAL FOR EXPANSION TO GENERALLY THE ORIGINAL MORE OPEN, LOW DENSITY STATE THEREOF. 